Week 2 Air standard Cycle

1. Your code should create a PV diagram

2. You should output the thermal efficiency of the engine.

""" 
otto cycle simulator
"""

import math
import matplotlib.pyplot as plt


def engine_kinematics(bore,stroke,con_rod,cr,start_crank,end_crank):
	"""
	engine_kinematics
	"""

	#geometric parameters
	a=stroke/2
	R=con_rod/a

	#volume comutation
	v_s=(math.pi/4)*pow(bore,2)*stroke
	v_c=v_s/(cr-1)


	sc=math.radians(start_crank)
	ec=math.radians(end_crank)

	num_value=50

	dtheta=(ec-sc)/(num_value-1)

	V=[]

	for i in range(0,num_value):
		theta=sc+i*dtheta
		term1=0.5*(cr-1)
		term2=R+1-math.cos(theta)
		term3=pow(R,2)-pow(math.sin(theta),2)
		term3=pow(term3,0.5)

		V.append((1 + term1 * (term2-term3))*v_c)

	return V

#inputs
p1=101325
t1=500
gamma=1.4
t3=2300

#geometric parameters
bore=0.1
stroke=0.1
con_rod=0.15
cr=13


#volume comutation
v_s=(math.pi/4)*pow(bore,2)*stroke
v_c=v_s/(cr-1)
v1=v_s+v_c

#state point 2
v2=v_c

#p2v2^gamma=p1v1^gamma
p2=p1*pow(v1,gamma)/pow(v2,gamma)

#p2v2/t2=p1v1/t1 |  rhs=p1v1/t1 | p2v2/t2=rhs |

rhs=p1*v1/t1

t2=p2*v2/rhs

V_compression=engine_kinematics(bore,stroke,con_rod,cr,180,0)

constant=p1*pow(v1,gamma)

P_compression=[]

for v in V_compression:
	P_compression.append(constant/pow(v,gamma))

# state point 3

v3=v2

#p3v3/t3=p2v2/t2 | rhs=p2v2/t2 | p3v3/t3=rhs |

rhs=p2*v2/t2

p3=rhs*t3/v3

V_expansion=engine_kinematics(bore,stroke,con_rod,cr,0,180)

constant=p3*pow(v3,gamma)

P_expansion=[]

for v in V_expansion:
	P_expansion.append(constant/pow(v,gamma))


# state point 4

v4=v1

# p4v4^gamma=p3v3^gamma

p4=p3*pow(v3,gamma)/pow(v4,gamma)

rhs=p3*v3/t3 
t4=p4*v4/rhs

plt.plot(V_compression,P_compression)
plt.plot([v2,v3],[p2,p3])
plt.plot(V_expansion,P_expansion,)
plt.plot([v4,v1],[p4,p1])
plt.show()